Research And Designon Fuel Management With Two Enrichment

Core fuel management of PWR is of great importance to insure the safety and economics of the nuclear power plant.The main target is to get a fuel management scheme which can improve fuel availability,reduce costs of fuel while the core safety is insured.The worldwide PWR power plants have extended the cycle length to increase the average assembly discharge burnup and improve the economics of power plant since 1980.Research and design on fuel management is performed in this work to achieve more exact assembly discharge burnup control and to improve fuel availability.Plenty of multi-cycle fuel management schemes are searched and calculated based on the Mega-kW PWR in which 157 assemblies are loaded.Relationships between recharged assembly number N,enrichment of new assembly?,cycle length T,average burnup of discharged assemblies BU_avg and maximum assembly burnup BU_max which affect the fuel management significantly are analysed according to the calculation results.A fuel management scheme using assemblies of two enrichments instead of single enrichment is introduced and a lot of search work is carried out.It is shown that utilization of assemblies of two enrichments can satisfy the cycle length demand accurately and provide a wider cycle length range,so that it helps to control cycle length and average burnup of discharged assemblies accurately in a flexible way during operation which improves the economics of the nuclear power plant.The fuel management scheme contains 3 transient cycles,1 equilibrium cycle and 4 flexible cycles.32 new assemblies with two enrichments?4.45%and 4.95%?are loaded in the equilibrium cycle.The cycle length reaches506 EFPD which is a long fuel cycle,while the BU_avg and BU_max of assemblies with enrichment of 4.95%are 48013 MWd/tU and 51486MWd/tU which indicate better plant economics.General key safety parameter calculations and power capability analysis have been done for the 8 cycles and the results indicate that the fuel management scheme in this work can meet the requirements on safety of the nuclear power plant operation.